Lock MacLeod suffered ankle ligament damage during the Celtic League game against Leinster and underwent further assessment on Monday.

Borders back-row team-mate Scott Gray missed a training session with the Scotland squad at Stirling after a knee injury, while Edinburgh forward Allister Hogg received further rehab on a knee injury.

Jason White and Tom Smith were also absent from training after suffering from flu-like symptoms.

Glasgow Warriors back-rower Andrew Wilson has been ruled out for a month after injuries to both knees in the European Cup defeat at Northampton earlier this month.

Williams could draft in Edinburgh pair Alasdair Strokosch and Simon Cross, as cover for the number of injuries in his back row.

Leeds Tykes flanker Jon Dunbar also trained with the squad but is still awaiting verification of his eligibility to qualify for Scotland, through a paternal grandmother and a maternal grandfather, who were both born in Edinburgh.